Process for oxidizing olefins to aldehydes, ketones and acids



Patented Oct. 9, 1962 3,057,915 PRGCESS FQR GXIDEZWG OLEFINS T ALDE-HYDES, KETONES AND ACiDS Wilhelm .iemenschneider, Lothar Hornig, ErhardWeber,

and Kurt Dialer, all of Frankfurt am Main, Germany, assignors toFarbwerke Hoechst Aktiengesellschaft vorrnais Meister Lucius & Eruning,Frankfurt am Main, Germany, a corporation of Germany No Drawing. FiledSept. 12, 1958, Ser. No. 760,539 Claims priority, application GermanySept. 14, 1957 6 Claims. (Cl. 260-533) The present invention relates toa process for oxidizing olefins to aldehydes, ketones and acids.

It has already been proposed to oxidize ethylene catalytically by meansof an argentiferous catalyst to ethylene oxide, or by means of anoxidation catalyst other than a silver-containing catalyst at a raisedtemperature to obtain mixtures of formaldehyde, acetaldehyde, formicacid, acetic acid and other products. These Processes, however, do notproduce acetaldehyde or acetic acid in a yield interesting for aneconomical point of view. Our experiments have revealed that theoxidation carried out under such conditions in the presence of a noblemetal catalyst likewise involves small yields of acetaldehyde, and therelative proportion of formaldehyde obtained generally preponderates.

It is also known that compounds of palladium, plati num, silver orcopper form complex compounds with ethylene. Furthermore, the formationof acetaldehyde was observed in decomposing a potassium-platinum-complexcompound. Other unsaturated compounds may favor the complex formation.In this case stoichiometric reactions are concerned yielding the noblemetal as such.

It has also been described to reduce palladous chloride by means ofethylene in the presence of Water to palladium metal. In this reductionthe formation of acetaldehyde was observed.

Still further, it has been described that palladous chloride dissolvedin water can be reduced rapidly and completely to palladium by means ofpropylene, even if propylene is admixed with nitrogen or air. It hasalso been described to reduce palladous chloride by means of isobutyleneunder the same conditions. It is, however, known that carbon dioxide isnot evolved either in this latter reduction or in those reductions whichare carried out in the presence of ethylene or propylene as a reducingagent.

In application Serial No. 747,115 in which two of the present inventorsare co-inventors, a process is described according to which carbonylcompounds can be obtained from the corresponding olefins in a good yieldand, if desired, in a continuous manner, by contacting said olefins withgaseous oxygen, water which is present in the vaporous form, and a solidcatalyst which contains a compound of the noble metals belonging togroup VIII of the periodic table as catalytic substance and a redoxsystem.

In the aforesaid application the term carbonyl compounds is used in itsbroad sense, i.e. it covers not only aldehydes and ketones but alsocarboxylic acids such as acetic acid.

According to the aforesaid invention there may be used as redox systems,for example, those which contain compounds of metals which under thereaction conditions employed may appear in various oxidation stages, forexample compounds of copper, mercury, cerium, thallium, tin, lead,titanium, vanadium, antimony, chromium, molybdenum, uranum, nickel, orosmium, and also inorganic redox systems other than specified above,such as sulfite/sulfate, arsenite/arsenate or iodide/iodine systemsand/or organic redox systems, for example ambenzene/hydrazobenzene, orquinones or hydroquinones of the benzene, anthracene-or phenanthreneseries.

As compounds of the noble metals of group VIII of the periodic tablethere may be used in the process of the aforesaid invention, forexample, compounds of palladium, iridium, ruthenium, rhodium orplatinum. Compounds of this series of metals are capable of formingaddition compounds or complex compounds with ethylene. If desired theoxygen may be used in admixture with an inert gas. The oxygen may beemployed, for example, in the form of air, which is the cheapestoxidizing agent. The use of air is, however, confined to certain limits,if the unreacted gases are circulated, inasmuch as nitrogen concentratesas ballast material. Instead of ethylene there may also be used a gasmixture containing ethylene and, for example, saturated hydrocarbons.The reaction may also be carried out in the presence of a noble metal.

The reaction may be supported or carried out by addition of an activeoxidizer, such as ozone, peroxidic compounds, especially hydrogenperoxide or sodium peroxide, potassium peroxide, potassium persulfate,ammonium persulfate, alkali percarbonate, alkali perborate, per-aceticacid, diacetyl peroxide, benzoyl peroxide, toluyl peroxide, oxygencompounds of nitrogen, such as nitrogen dioxide and nitrogen pentoxideor mixtures of nitrogen oxides containing the same, nitryl halides suchas nitryl chloride, free halogen such as chlorine, bromine, orbromotrichloride, halogen-oxygen compounds such as chlorine dioxide,hypochlorous acid, chloric acid, perchloric acid, bromic acid, iodicacid, periodic acid, or compounds of the higher valence stages ofmetals, such as manganese, cerium, chromium, selenium, lead, vanadium,silver, molybdenum, cobalt, or osmium, for instance potassiumpermanganate, sodium bichromate, lead tetraacetate, vanadium pentoxide,silver difluoride, selenium dioxide, cerium-(IV)su1fate, osmiumtetroxide. The addition of an active oxidizer facilitates there-formation of the higher oxidation stage of the active catalystcomponent which is necessary for carrying out the reaction. Theseoxidizing agents may also be produced during the reaction. If desired,an oxidizing catalyst may be added.

In the reaction described in the aforesaid application it is oftenadvantageous to add, prior to or during the reaction, a compoundyielding anions under the reaction conditions applied, for example aninorganic acid, preferably a mineral acid such as sulfuric acid, nitricacid or a volatile acid such as hydrochloric acid or hydrobromic acid ora salt such as ammonium chloride, ammonium bromide, zinc chloride,aluminum chloride, iron chloride, chromic chloride, titaniumtetrachloride, sodium hydrosulfate, a halogen or a halogen-oxygencompound, for example those mentioned above, or thionyl or sulfurylchloride, or also an organic substance, preferably a saturated aliphatichalogen compound of low molecular weight such as ethyl chloride, propylchloride, butyl chloride, acetyl chloride, benzoyl chloride, propionylchloride, phosgene. Such addition enables a possible decrease of anionsto be counteracted and the lifetime of the catalysts to be prolonged.

In case that non-volatile compounds yielding anions are used as listedabove, these substances are, of course, added to the catalyst before thereaction, while the volatile compounds can be added as well before asduring the reaction.

The aforesaid process is carried out in the presence of a solid catalystat relatively low temperatures. Suitable contact supports (carriers)are, for example, silica gel, kieselguhr, pumice, silicates, TiO A1 0active carbon, acid ion exchangers, such as Amberlite IRC 50, Dowextypes 50, Permutites, phenol-aldehyde-resins which are substituted bysulfonic acid groups, polystyrene-resins which are substituted bysulfonic acid groups and crosslinked by divinyl-benzene, etc., ormixtures of such carriers.

The aforesaid process can be carried out with special advantage attemperatures within 50 C. and 160 C., preferably 50 C. and 100 C.; ifdesired, the process may also be carried out at temperatures outside theranges indicated above, for example at 170 C. to 180 C., or for exampleat 40 C., or within a range of, for example, 80 C. and 120 C. It isfurthermore of importance to carry out the process in an acid to neutralmedium. The preferred pH-values are within 0.8 and 3; higher pH- valuesbetween, for example, 0.8 and 5 or 2 and 6, or lower pH-values of, forexample, 0.5 may also be used, although such pH-values generally do notinvolve a special advantage. In the said reaction the solution withwhich the solid catalyst is impregnated may be adjusted so as to have apH within the limits indicated above.

In the aforesaid process sometimes the presence of a salt, such assodium chloride or potassium chloride like that of hydrochloric acid orof other alkali metal or alkaline earth metal halides such as LiCl, CaClor other salts such as CuCl or ZnCl may prove advantageous. By thepresence of these salts, for example the reactivity of CuCl, which maybe formed in the course of the reaction, may be improved.

The aforesaid process can be carried out at atmospheric pressure, undera raised pressure and under reduced pressure, that is, under a pressureof up to 100, preferably of up to 50 atmospheres gauge. The process maybe carried out under pressure regardless of whether the temperaturesused are above or below 100 C.

The reaction may be supported by increasing the ethylene and/or oxygenconcentration in the reaction space. This can be achieved, for example,by increasing the pressure. The ethylene concentration at the surface ofthe catalyst may be considerably increased, for example, by using higherconcentrations of metal salts binding ethylene, for instance copper-,iron-, mercuryor iridiumcompounds, especially halides, or the sulfates,the latter especially when mercury is concerned. The gases may becirculated, for example a gas containing a few percent of unreactedoxygen.

Due to the presence of oxidizing agents acetic acid may be formed in asmall amount in addition to acetaldehyde. If desired, the oxidation ofacetaldehyde to acetic acid which is known in the art, may be combinedwith the reaction described above in order to omit partially or totallythe aldehyde stage, or acetaldehyde may be oxidized in a second stage toacetic acid.

It is described in the aforesaid application that under the conditionsspecified above under which ethylene yields acetaldehyde, propyleneyields preponderantly acetone and propionaldehyde. ocand fl-butyleneyield preponderantly methylethyl ketone, the u-butylene yielding alsobutyraldehyde, and isobutyraldehyde can be obtained from isobutylene.

In the case Where higher olefins are concerned, such as pentene and itshomologs, cyclohexene or styrene, the reaction proceeds substantially ina manner analogous to that described and it can be carried out under thesame conditions as set forth above. Due to the relatively mild reactionconditions there are almost exclusively obtained those oxidationproducts which had to be expected in view of their structure, withoutnoteworthy isomerizations or molecule decompositions occurring.

Mixtures of olefins or gases containing olefins or other unsaturatedcompounds may be reacted in the same manner, provided they are capableof reacting under the reaction conditions, for example diolefins. Thereaction of olefins containing 2 to 3 carbon atoms is, however,preferred. Under circumstances, the reaction conditions must be adaptedto the compounds used and to their physical properties. The higherboiling points of the reaction products may also require a correspondingmodification of the reaction conditions. Diacetyl may be obtained, forexample, from butadiene.

For stoichiometric reasons the molar ratio of olefin bond to oxygen mustbe 2:1 in the complete oxidation of olefins to the correspondingaldehydes or ketones. To prevent explosions, it is, however, preferredto use an oxygen deficiency, for example in the range of 2.5 :1 to 4:1.Still further it is preferred to work outside the range of explosivity,for example with a content of oxygen of 8-20 percent or 8l4 percentunder pressure, and to circulate unreacted gas especially thatconsisting of olefin in excess or other inert gases, such as nitrogen;oxygen and ethylene are restored as they are consumed.

Now we have found that in the above process the yield of acids whichcorrespond to the aldehydes, can be considerably increased without thealdehyde yield being reduced, when an olefin is contacted with gaseousoxygen in the presence of water vapor at a solid acid to neutralcatalyst comprising a carrier, a compound of a noble metal of group VIIIof the periodic system and a redox system containing one or morecompounds of one or more metals having an atomic number in the rangefrom 25 to 27, ie iron, manganese and/ or cobalt. This eltect isunexpected inasmuch as it was supposed that part of the aldehyde formedwould be oxidized in the catalyst to the corresponding acid; it couldnot be foreseen, however, that an additional amount of acid would beformed.

The compounds of iron, manganese or cobalt are added to the catalyst inthe usual manner. It is possible, for example, to impregnate thecatalyst with the soluble salts of these elements and to convert thesesalts by heating, preferably with air, to the firmly adhering oxides.There may also be used a mixture comprising the aforesaid compounds.

The acid formed can be readily separated from the correspondingaldehyde. According to the present invention, it is preferred toconcentrate the acid, which has always a boiling point higher than thealdehyde, in a first separator, and to concentrate the aldehyde whichhas a boiling point lower than the acid, in a second separator. Bothseparators are connected in series.

The simultaneous production of carboxylic acids and aldehydes at solidcatalysts containing an iron-, manganeseand/or cobalt salt, ispreferably carried out in the presence of further redox systems, such ascopper compounds.

The process of this invention is generally carried out with thecatalysts and under the conditions broadly described in application Ser.No. 747,115 and referred to above, preferably by contacting the olefinand oxygen or air simultaneously with the catalytic substances.

In a frequently useful technical variant of the process of thisinvention the desired reaction products, for ex ample acetaldehyde andacetic acid, are separated from the reaction gas, the residual gas whichmay contain inert gases and may be free from oxygen, but may likewisecontain some oxygen, is reintroduced and an amount of olefin and oxygencorresponding to that consumed during the reaction is introduced intothe reactor through one or more inlets, which may be arranged one abovethe other or one behind the other or the olefin and/or the oxygen areadded to the circulating gas. For example, the residual gas is admixedwith an amount of ethylene r corresponding to that consumed, and theresulting gas mixture, containing, for example, -95 percent of olefin(for example ethylene) and l0-5 percent of ox gen, is introduced intothe reactor as well as an amount of oxygen corresponding to thatconsumed. For the sake of security the oxygen, if desired in admixturewith inert gases such as present in air is preferably introduced throughseparate inlets, especially when no diluting gas is present and aboutstoichiometric amounts of the reactants are applied.

In order to obtain especially high space-time-yields, it is alsopossible to introduce either olefin or oxygen, or

.5 olefin and oxygen into the reaction vessel, for example a reactiontower, at various places arranged one above the other or one behind theother. Preferably the inlets for each reactant are locally separatedfrom the other inlets for the same reactant. It is likewise possiblethat the amount of oxygen introduced is measured so as to keep at allplaces of the reaction vessel below the lower limits of the explosiverange.

In many cases the reaction proceeds likewise smoothly if the catalystsused contain only a small amount of compounds of the noble metalsbelonging to group VIII of the periodic table. In most cases it issufiicient to use a catalyst in which the ratio of the sum of the redoxmetals, especially the sum of copper and iron to the noble metal,especially palladium, is at least 15 1, preferably 25-500: 1. It is,however, preferred to use a catalyst containing copper salts, in whichthe ratio of copper to palladium is above :1, for example above :1 andpreferably 50:1 to 500:1, or even above these ranges. This method ofoperating is more economic in view of the fact that the expensivepalladium salt need only be used in a minor amount; it can be used forconverting ethylene and olefins other than ethylene, and may be combinedas desired with variants hereinbefore or hereinafter described. Thisembodiment may also be carried out under elevated pressure.

As stated above the escaping reaction gases may be reused or circulated.Furthermore the reactants may be diluted by gases inert towards thereaction, for example by nitrogen, carbon dioxide, methane, ethane,propane, butane, isobutane and other saturated aliphatic com pounds, andfurthermore by other compounds, such as cyclohexane, benzene or toluene.

The reaction of the present invention is favourably influenced byirradiation with rays rich in energy, preferably ultraviolet light. Suchirradiation which may also comprise X-rays activates especially theoxygen, increases its oxidation activity, and promotes both the reactionwith the olefin and a possible oxidative destruction of byproducts, forexample oxalic acid. These measures increase the conversion, reduce theformation of by-products and considerably prolong the lifetime of thecatalyst, the activity of which may subside after a prolonged time.

In practice it is advantageous to use a mercury quartz lamp as source ofradiation arranged in the catalyst so that the light energy is fairlysubstantially utilized. If the reaction is carried out with an apparatusinto which oxygen or an oxygen-containing gas is introduced separatelyfrom the olefin or olefin-containing gas or even an olefin-oxygenmixture, it is preferred to arrange the source of radiation in thevicinity of the oxygen inlet, so that that part which is rich in oxygenis especially well irradiated. The oxygen is thereby activated as longas it has a high partial pressure. In an apparatus in which the catalystcirculates, it is advantageous to arrange the source of radiation at thelower end of the contact line, immediately above the oxygen inlet.Activation may also be brought about by adding a compound of aradio-active element to the catalyst solution.

The conversion and the space-time-yield in the present reaction depend,for example, on the residence time in the gases through a tube which isfilled with the catalyst,

or with the use of a fluidized bed catalyst. Condensates which separatefrom the reacted gas, especially aqueous condensates, may also berecirculated after vaporization to again participate in the reaction,for example as such or after separation of higher and/or lower boilingreaction products.

It is not necessary that the catalysts used are made of fine chemicals;they may likewise be produced from suitable metals of commercial purity.Metals, such as copper and iron may be readily dissolved even bynotoxidizing acids, such as hydrochloric acid and acetic acid, ifdesired by addition of an oxidizing agent if copper is used, or bypassing through during the dissolving process a gaseous oxidizingmedium, such as oxygen or air enriched with oxygen. The contaminationscontained in commercially pure metals do not affect the reaction if thesolutions obtained are worked up to the solid bed cataylsts used in theprocess of the present invention. More especially the catalytic activityremains practically unaffected by small amounts of foreign metals whichmay appear in copper or iron of commercial purity. The anion formingagents contained in metals, such as sulfur, phosphorus, carbon,silicium, etc., are converted upon being dissolved to either hydrogencompounds, for example H 8, which escape together with the reactiongases, or oxidized to acids of a higher valence stage, for example Hwhich do not affect the reaction, or are converted partially intoinsoluble compounds, for example CuS, which appear only in minor amountsand, if necessary, can readily be separated from the catalyst, forexample by filtration, before the catalyst solution is applied to thecarrier.

The solutions so obtained are then admixed with the noble metal compoundwhich is added in substance or in the dissolved state, if desireddiluted with water, and the concentration of hydrogen ions is adjustedto the degree desired; the solutions so prepared may then beconcentrated and are applied to a carrier, for instance those mentionedabove.

Solvents suitable for dissolving the metals are chiefly hydrochloricacid and acetic acid in view of the fact that the presence of theseacids proves especially advantageous in oxidizing olefins to aldehydes,ketones and acids. Acids other than those indicated above may, however,also be used, for example nitric acid. In this case, it is preferred toremove the acid in excess in order to adjust the solution to the pHdesired and to use the solution so treated for impregnating the carrier.If desired the salt of the metals may partially be converted into thecorresponding chlorides and/ or acetates.

Palladium chloride or other noble metal chlorides need not be used;there may also be employed the metals themselves, e.g. metallicpalladium, suitably in a finely divided and finely distributed state,which reacts, for example, with copper chloride, and is converted topalladium chloride or a compound other than palladium chloride.

For example, the catalyst may contain as anion chlorine ions or halogenions other than chlorine, such as fluorine or bromine ions, nitrates orchlorateor perchlorate radicals, or mixtures of these anions, forexample, with sulfate or acetate radicals. Sometimes it is especiallyadvantageous to use a catalyst which contains perchlorate ions.

Although the catalysts have generally a good activity even after aprolonged time of reaction, especially when anions are added during thereaction, it may be advantageous to regenerate the catalyst from time totime. Some variants for such regeneration are described hereinafter.

It may be that the activity of the catalyst, especially when thecatalyst is used for a very long period of time, is more or less reducedby the formation of a minor amount of by-products, or by foreignsubstances which may have been introduced. The by-products formedconsist partially of organic compounds which are watersoluble at leastto a certain degree, such as acetic acid, oxalic acid, higher aldehydesor ketones or chlorinated organic compounds. Foreign substances possiblyintroduced into the catalyst may derive from, for example, con- 7taminations of the gases, or the corrosion of parts of the apparatus,for example, of iron parts or of the lining of the reactor. 1

The catalyst may be freed from these contaminations and regenerated in asimple manner by precipitating the cupric chloride as cuprous chlorideand the noble metal compound as elementary metal. The precipitation maybe effected directly on the carrier or the catalytic compounds may bedissolved therefrom. Precipitation is preferably carried out with theexclusion of substantial amounts of oxygen by the action of carbonmonoxide, hydrogen or one or more olefins, for example ethylene,propylene or the butylenes, or of any other olefin or a mixture ofseveral of these precipitating agents. The mixture of cuprous chlorideand noble metal or the solid catalyst in which these substances areprecipitated are advantageously washed, e.g. with water. If a solutionof the catalytic agents had been prepared it is mixed with water and anacid, suitably hydrogen chloride, if desired in the form of hydrochloricacid, and may, after a salt of iron, manganese and/or cobalt has beenadded, be reused in the impregnation in this state or, if desired, afteroxidation with oxygen or an oxygen-containing gas, such as air. If thecuprous chloride and the noble metal are precipitated in the carrier,the washed carrier is treated with a solution of a salt of iron,manganese and/or cobalt and with an acid, such as hydrochloric acid and,if desired, is additionally oxidized, e.g. by means of oxygen orchlorine, and then reused. If a separate oxidation is dispensed with anolefin and oxidation agent are allowed to act simultaneously upon thecatalyst to be reused, oxidation is brought about in the followingreaction by the oxygen contained in the reaction gas. After theregenerated but not yet oxidized catalyst has been reintroduced into thereactor, the amount of oxygen contained in the reaction gas maytemporarily be increased, if desired. If in reducing the catalyst oxygenis not completely excluded, it is only necessary to use a somewhatlarger amount of reducing agent.

This mode of execution is especially interesting if in addition to thenoble metal the catalyst contains substantial amounts of copper salts,since these two rather expensive components of the catalystCuCl andnoble metalprecipitate, while all other impurities or additions, forexample iron salts, remain in the solution and are thus separated fromthe expensive noble metal and copper compound.

The noble metal is quantitatively precipitated as well as CuCl, exceptfor a minor amount thereof which is soluble in water. In reusing thecatalyst it is therefore advisable to add the corresponding amount offresh CuCl and/or CuCl+HCl. The further well soluble and freqently cheapadditions, such as iron salts, are suitable to be replenished.

The simplest manner of allowing CO and/or olefins and/or hydrogen to actupon the catalyst is to introduce these substances upon the catalyst orinto the solution prepared as described above. In most cases this may bedone under normal conditions, but it may be advantageous to use a highertemperature and/or a raised pressure. More severe conditions areopportune, especially when hydrogen is used, which is the weakestreducing agent among the substances mentioned above. In using olefins asreducing agents the oxidizing activity of the catalyst may be used for afurther formation of aldehydes, ketones and acids.

It is furthermore advisable prior to allowing the above gases to actupon the solution which is obtained by dissolving the active componentsfrom the carrier to entirely or partially neutralize or buffer the acidcontained therein to a relatively low pH which is preferably in therange between 2 and 4. At too strong an acidity the reaction proceedstoo slowly or is incomplete after the usual time of reduction. Inaddition thereto, CuCl is remarkably soluble in concentratedhydrochloric acid, which may involve losses of copper. It should benoted that a further amount of hydrochloric acid is formed during thereduction of the copper or noble metal chloride, and this amount of acidmust possibly also be neutralized or buffered. Reduction at a pH higherthan 4 is often regarded to be disadvantageous since hydroxides arelikewise precipitated, though a regeneration by precipitating thehydroxides or basic salts of the metals used is likewise possible.

Neutralization or buffering may be made in the usual manner withalkaline reacting substances, such as sodium hydroxide solution, sodiumcarbonate, sodium acetate, chalk, lime, and similar compounds. The saidreducing gases may be circulated for reasons of economy and, especiallyif carbon monoxide is used, may also be subjected to a C0 wash.

According to another method of regeneration of the solid bed catalyst,the olefin supply may be arrested for a short While and the catalyst maybe treated simultaneously with oxygen or oxygen-containing gases andsteam and an acid in vapor form or gas form, preferably hydrogenchloride or hydrogen bromide. A variant of such regeneration consists,for example, in passing oxygen or an oxygen-containing gas partially orcompletely and prior to contacting the catalyst through aqueoushydrochloric acid, preferably at a raised temperature. Accurately dosingthe hydrochloric acid is especially simple, if a 20 percent hydrochloricacid is used.

The catalyst which prior to this treatment has possibly a metallicglance turns again brown and regains its initial activity, possiblyafter an induction period of several hours.

The apparatus used in the process of this invention should be made of amaterial which has a suificient ther mal conductivity and is notcorroded by the catalyst. Since the catalysts used contain noble metalcompounds, for example palladium compounds, it is less suitable to usethe usual metals and alloys as construction material, since there is therisk that these less noble metals, in the presence of water and at theindicated temperatures, precipitate the noble metal salt used in thecatalyst, and that they themselves are converted into salt form.

In order to avoid corrosion in the apparatus used, it is often suitableto use an apparatus lined with titanium or titanium alloys containing atleast 30 percent of titanium,

' or with tantalum. There may also be used glass vessels or enamelled orrubber-lined vessels. The reaction may also be carried out inbrick-lined vessels or, under suitable reaction conditions, in vessels,the insides of which are lined with plastic material, for examplepolyolefins, polytetrafiuorethylene or hardenable unsaturatedpolyesters, or phenol-, cresolor xylenol-formaldehyde resins. As bricklining there may be used, for example, ceramic material, carbon bricksimpregnated with hardenable artificial resins and similar knownmaterials.

The following examples illustrate the invention but they are notintended to limit it thereto.

Example I 3.3 grams of Mn(NO .6H O are dissolved in 30 cc. of water andthe solution so obtained is used to impregnate 100 cc. of silica gel.Silica gel so pretreated is heated for about 3 hours at 250300 C. in afurnace in the presence of a weak current of air. The cooled catalyst isimpregnated with a solution of 2 grams of PdCl and 19.5 grams of CuCl.2H O in 30 cc. of water, and is ready for use after having been driedfor about 1 hour at C.

80 cc. of the catalyst prepared as described above are heated at 80 C.in a contact tube and a mixture of 10 liters of ethylene and 3.3-4.0liters of oxygen is passed through per hour. The gases introduced intothe furnace are saturated with Water at a temperature of 80-85 C., orwater is added dropwise in an amount corresponding to that entrained bythe escaping gases. Acetaldehyde is obtained in a yield of 4550 percentand acetic acid in a yield of 15-20 percent, calculated upon theethylene used.

The escaping gases consist of unreacted ethylene and a minor amount ofoxygen; they are capable of being circulated.

Example 2 10 liters of ethylene and 3.5 liters of oxygen are passed, ata contact temperature of about 90 C., through 240 cc. of a catalystcontaining 10- grams of PdCI 38 grams of CuCl and 18.3 grams of FeCl;,per liter of silica gel (carrier). The gas. mixture used has previouslybeen saturated with steam at about 70 C.

Highly concentrated acetic acid is obtained in a heatable separatorprovided with a reflux condenser and connected in series with thecontact tube. Acetaldehyde is separated from the gas current by a waterwash. The conversion, calculated upon the amount of ethylene used, is30-35 percent of acetaldehyde and 10-15 percent of acetic acid.

Similar results are obtained by using the same amount of granular activecarbon as a carrier instead of silica gel.

Example 3 3.3 grams of Mn(NO .6H O and 3.5 grams of Co(NO .6H O aredissolved in 25 cc. of water and the solution obtained is used toimpregnate 100 cc. of silica gel. The silica gel is then treated for 2to 3 hours in a furnace at 250-300 C. with a current of air to form themanaganese and cobalt oxides on the carrier. The catalyst so pretreatedis impregnated with a solution of 2 grams of PdCl and 19.5 grams of CuC1.2H O in 30 cc. of water and dried for a short period at 80 C.

A gas mixture of 10 liters of ethylene and liters of oxygen which haspreviously been saturated with water at 8082 C. is passed per hour overthe catalyst while the outer temperature of the contact furnace ismaintained at 80 C. The reaction gases are condensed and washed to yield40-50 percent of acetaldehyde and -13 percent of acetic acid, calculatedupon the ethylene used. A fresh catalyst yields initially onlyacetaldehyde. The formation of acetic acid sets in only after 10-12hours and reaches the above rate after a further 3-5 hours. Theconversion rate decreases after a period of some days and reaches theinitial height by an incidental or continuous addition of hydrogenchloride, if desired in the form of evaporated hydrochloric acid.

Example 4 1.76 grams of Co(NO .6H O are dissolved in 30 cc. of water andthe solution obtained is used to impregnate 100 cc. of silica gel. Thecobalt oxide is produced as indicated in Example 2 and the catalyst istreated in the manner described in the preceding example with 2 grams ofPdCl- 19.5 grams of CuCl .2H O and 4.6 grams of MgCl .6H O.

A mixture of 10 normal liters of ethylene and 2.5 normal liters ofoxygen (N.T.P.) is passed per hour over the catalyst under a pressure of1 atmosphere gauge and at a furnace temperature of 80 C. The fresh gascurrent is simultaneously admixed per hour with 5-10 cc. of water. Theconversion, calculated upon the ethylene used, is about 30 percent foracetaldehyde and about 10 percent for acetic acid. In this example, too,acetic acid is only formed after a period of about 10 hours. The rate ofconversion remains constant for a prolonged time and is later kept atthis level by cautious addition of dilute hydrochloric acid instead ofwater.

We claim:

1. In the process for the conversion of ethylene into a carbonylcompound selected from the group consisting of acetaldehyde and aceticacid by contacting ethylene in a reaction zone in the presence of watervapor with gaseous oxygen at an acid-to-neutral solid catalystcomprising a carrier, a salt of a noble metal of group VIII of theperiodic system the stable valence of which is at most 4, and cupricchloride, the improvement of contacting the reactants with a catalystwhich additionally contains an oxide of at least one metal having anatomic number from 25 to 27.

2. A process as defined in claim 1 wherein strong vaporizable inorganicacids are supplied to the catalyst during the reaction.

3. A process as defined in claim 1 wherein said salt of a noble metal isa palladium salt.

4. A process as defined in claim 1 wherein the reaction is carried outat a temperature in the range between 40 and C. and the catalystcomprises a carrier, palladium chloride, cupric chloride, and an oxideof at least one metal having an atomic number from 25 to 27, wherein acompound yielding chloride ions under the reaction conditions issupplied to the catalyst during the reaction, and wherein non-convertedgaseous compounds are recycled from the reaction zone back into thereaction zone after the substantial separation therefrom of carbonylcompounds produced and with the addition of more ethylene and oxygenthereto.

5. A process as defined in claim 1 wherein the oxygen and the ethyleneare reacted in the presence of a diluent consisting of a member selectedfrom the group excess ethylene, gases inert under the reactionconditions applied, and mixtures thereof.

6. A process as defined in claim 1 wherein ethylene is intermittentlyintroduced into the reaction zone and the catalyst is contacted withoxygen, steam and vaporized acid when ethylene is absent.

References Cited in the file of this patent UNITED STATES PATENTS1,999,620 Van Peski et a1 Apr. 30, 1935 2,055,269 Van Peski et al Sept.22, 1936 2,333,216 Trieschmann et al Nov. 2, 1943 2,451,485 Hearne et alOct. 19, 1948 2,486,842 Hearne et a1 Nov. 1, 1949 2,690,457 HackmannSept. 28, 1954 2,776,316 Baldwin Jan. 1, 1957 FOREIGN PATENTS 575,571Great Britain Feb. 25, 1946 664,879 Germany Sept. 16, 1958 722,707Germany July 27, 1942 OTHER REFERENCES Karrer: Organic Chemistry, 4thed. (1950), page 504.

1. IN THE PROCESS FOR THE CONVERSION OF ETHYLENE INTO A CARBONYLCOMPOUND SELECTED FROM THE GROUP CONSISTING OF ACETALDEHYDE AND ACETICACID BY CONTACTING ETHYLENE IN A REACTION ZONE IN THE PRESENCE OF WATERVAPOR WITH GASEOUS OXYGEN AT AN ACID-TO-NEUTRAL SOLID CATALYSTCOMPRISISNG A CARRIER, A SALT OF NOBLE METAL OF GROUP VIII OF THEPERIODIC SYSTEM THE STABLE VALENCE OF WHICH IS AT MOST 4, AND CUPARAICCHLORIDE, THE IMPROVEMENT OF CONTACTING THE REACTANTS WITH A CATALYSTWHICH ADDITIONALLY CONTAINS AN OXIDE OF AT LEAST ONE METAL HAVING ANATOMIC NUMBER FROM 25 TO 27.